Behavioral correlates of tooth eruption in Madagascar lemurs.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 66:307-315 (1985)
Behavioral Correlates of Tooth Eruption in Madagascar Lemurs
ROBERT H. EAGLEN
Department of Anatomy, University of Puerto Rico, Medical Sciences
Campus, Sun Juan, Puerto Rico 00936
KEY WORDS
Dental eruption, Lemurs, Feeding behavior, Growth
ABSTRACT
Observations on the sequence and timing of gingival tooth
eruption are reported for six species of Madagascar lemurs. Complete sequences of eruption were obtained for the deciduous dentition, and partial to
complete sequences were recorded for the permanent dentition. In CheirogaZeus medius and in four species of the genus Lemur, the deciduous teeth erupt
in front-to-back sequence, with the toothcomb emerging near birth as an
integrated complex. In Propithecus verreauxi the same pattern is exhibited,
but the small peglike lower canine and dp3 erupt last. Eruption of the permanent dentition in Lemur species takes place in two distinct stages. In the first
stage the upper incisors, toothcomb, and first two molars penetrate the gingiva.
After a n interval of 3 to 4 months, the remaining permanent teeth erupt.
Deciduous premolars erupt when young animals are being weaned. The
eruption of the deciduous toothcomb appears unrelated to feeding or grooming
behavior. In L. catta and L.fulvus, the first stage of permanent tooth eruption
occurs at approximately 6 months of age, when the growth rate slows down
and (in wild populations) the rainy season is ending. This suggests that eruption of the anterior molars is timed to coincide with a shift from a more
frugivorous to a more folivorous dietary regime, which occurs during the dry
season. No further tooth eruption occurs until approximately 1 year of age,
when the growth rate increases and the rainy season returns for wild populations. Thus, the second wave of permanent tooth eruption in these species
again appears linked to changing climatic conditions which lead to a shift in
dietary preferences.
Previous studies of dental eruption among
MATERIALS AND METHODS
nonhuman primates have tended to focus on
Most of the data reported here were obone of two aspects of the data. Some studies tained by physical examination of the oral
(e.g., della Serra, 1952; Schwartz, 1974) have cavities of live animals. From February 1977
concentrated on the phylogenetic implica- through August 1978, using the resources of
tions of dental eruption sequences, while the Duke University Center for the Study of
others (e.g., Tappen and Severson, 1971; Re- Primate Biology and History, I examined the
lethford et al., 1982; Glassman, 1983) have dentitions of growing lemurs (Table 1). Leemphasized the use of dental eruption se- mur and Propithecus subjects were examined
quences and eruption timing for the estima- once every 2 weeks; Cheirogaleus subjects
tion of chronological age. In this report I were examined twice each week. During each
present data on the sequence and timing of examination, the subject was weighed. The
dental eruption among some Madagascar le- relative states of eruption of individual teeth
murs, with a rather different emphasis; my were estimated by visual inspection of the
primary purpose is to relate certain aspects
Received November 28, 1983; revised February 27, 1984; acof Iemuroid dental eruption to emerging and cepted
March 8,1984.
mature behavioral patterns.
Duke University Primate Center Publication No. 264.
0 1985 ALAN R. LISS, INC.
308
R.H. EAGLEN
duous dentition of each species used in this
study. As those sequences indicate, there is a
reasonably homogeneous pattern within each
jaw as to the sequence in which lemur teeth
erupt. For all species of the genus Lemur
described in this study, the mandibular deciduous dentition erupts in a front-to-back sequence, with the toothcomb emerging as a
functional unit. The premolar eruption sequence indicated here is identical to the alveolar eruption sequences described by
Schwartz (1974) for the same species.
A similar pattern occurs in Cheirogaleus
medius. The only difference between this
species and the genus Lemur is that the posterior deciduous premolar appeared to be
more completely erupted than the middle
premolar a t the time these teeth were first
seen. Schwartz (1974) inferred a 2-4-3 sequence of deciduous premolar eruption for C.
medius. While his sequence is different than
that reported here and may indeed be technically correct, I should also note that the
middle and posterior premolars made their
first appearance simultaneously, and the difference in their respective crown heights was
RESULTS
not particularly striking. From a functional
Deciduous eruption sequences
point of view, tbe contradiction in the two
Table 3 summarized the inferred sequence eruption sequences is not likely to have any
and timing of gingival eruption for the deci- great significance.
oral cavity, sometimes with the aid of a Beebe
magnifying binocular loupe. After weighing
and oral examination, each subject was returned to its social group.
A simple scoring system was used to estimate the degree of dental eruption. A tooth
was scored as 0 (newly erupted) when it first
appeared to penetrate the surrounding gingival tissue. It was scored as 1in subsequent
inspections if the complete crown surface was
visible above the gingival plane, but the tooth
was lower in crown height than adjacent
teeth of equivalent size. A tooth was scored
as 2 (fully erupted) if the complete crown
surface was visible and it either exceeded the
height of adjacent teeth scored as 1, or
equaled the height of adjacent teeth scored
as 2.
Additional observations on the eruption of
the deciduous dentition were obtained by examining the oral cavities of deceased infants
and juveniles, and by fortuitous examination
of some live animals removed from their social groups for weighing and permanent
identification marking (Table 2).
TABLE I . Subjects
used i n contmuine xtudv
Species
Lemur catta
L. fuluus
L. macaw
L. uariegatus
Propithecus uerreauxi
Cheirogaleus medius
'Twins.
'Triplets.
ID No.
Sex
Study dates_-
2583
3547
3592
2586
2589
3556
3585
3504
3548l
3549l
3555
3509
3514
3557l
3558'
3580'
3581'
3582'
1593
632
633
F
M
F
F
F
M
M
F
M
M
M
F
M
F
M
F
F
M
M
F
M
3122177-8131178
4127178-8125178
6112178-8125178
4107177-8/31/78
4107177-8131178
4114178-813 1178
5130178-8131178
412 1177-8131178
4110178-8114178
4110178-8/14/78
4114178-8131178
5119177-8131178
5119177-8/31/78
4114178-8125178
4114178-8125178
6102178-8125178
6102178-8/25/78
6102178-8125178
2115177-7114177
6129178-8131178
6126178-8131178
Age span
during study
(days) 10-509
31-151
25-99
20 -531
21-532
11-150
24-117
27-524
11-137
11-137
13-152
30-499
28-497
10-143
10-143
29-113
29-113
29-113
9-158
10-73
7-73
309
TOOTH ERUPTION IN LEMURS
TABLE 2. Subjects examined fortuitously
ID No.
Species
Sex
Date
examined
~
Lemur catta
L. fulvus
L. uariegatus
2502'
35442
35452
1553'
2546'
2570'
3567
3542
3541
3539
1557'
1560'
1574'
2562'
2564'
3573
M
F
F
F
M
F
623'
636
627
M
M
Cheirogaleus medius
F
F
F
M
F
M
M
F
M
M
2/11/77
4/14/78
4/14/78
2/11/77
2111177
2/11/77
5/10/78
4/14/78
4114178
4/14/78
2/11/77
2/11/77
2/11/77
2/11/77
211 1/77
6/12/78
6/22/78
2/11/77
6/26/78
7/07/77
7/14/77
Age when
examined
(days)
1
18
18
21
1
13
22
24
25
26
36
86
133
0
46
50
60
2
7
9
16
'Cadaver.
'Twins.
TABLE 3. Sequence and timing of deciduous tooth eruption'
Species
Lemur catta
L fuluus
L. macaco
Week 1
Week2
Latest age of gingival eruption
(end of each respective week)
Week3 Week4
Week6
Week8
Week 10
tc
C
tc
?
?
L. uuriegatus
c-5
Propithecus uerreauxi
Cheiroguleus medius
(C,P4)
0
C
(P2,P3.P4)
O G a -
(il,i2)
'tc, deciduous toothcomb; lower "canine" of J? uerreauxi is the equivalent of dp, recognized by Schwartz (1974). Teeth grouped in
parentheses emerged "simultaneously,"i.e., on day of observation; sequencing within parenthetical groups inferred from differences
in crown height at time of first observation.
Propithecus verreauxi also shows a mesiodistal sequence of eruption for the mandibular deciduous dentition, but only for those
teeth which serve as functional units in occlusion. The rudimentary, peglike lower canine and dps erupt at a later date than the
remaining mandibular teeth. Since the former teeth are quite small, it is quite possible
that alveolar eruption sequences may differ
from gingival eruption sequences.
A slightly different but relatively consistent pattern characterizes the eruption sequence of the maxillary deciduous dentition.
For most species described here, the upper
deciduous canine is the first maxillary tooth
to erupt, followed in sequence by the anterior, middle, and posterior premolars. In most
cases, the lateral upper incisor is next to
erupt, followed by the central upper incisor;
in L. fulvus and €? verreauxi, however, one or
310
R.H. EAGLEN
both of the deciduous upper incisors may
penetrate the gingiva before all premolars
have begun their eruption. The lateral upper
incisor was always seen before the central
upper incisor, but incisors a s a group were
variable both within and between species in
terms of their timing of eruption relative to
the premolar complement. The difference in
the sequence of incisor eruption between upper and lower jaws could well be a reflection
of the diminutive size of upper incisors among
lemurs, and again it would not be surprising
if other investigators reported contradictory
sequences on the basis of alveolar eruption.
With few exceptions, any given mandibular deciduous tooth erupts earlier than its
maxillary counterpart. A similar phenomenon has been documented in the deciduous
eruption sequences of Saguinus fuscicollis
(Glassman, 1983) and S. nigricollis (Chase
and Cooper, 1969). Those studies also note a
mesiodistal progression in the sequence of
eruption of deciduous teeth, similar to the
pattern inferred for the lemur species described here.
Table 3 also gives the ages at which teeth
erupt. The ages reported are for initial eruption (i.e., the latest age a t which a tooth initially penetrates the gingival tissue). While
it might be more interesting to use the age
a t which a tooth were fully erupted, and
hence formed part of a functioning occlusal
unit, I have not reported the data that way
because my criterion for complete eruption is
somewhat arbitrary, while the criterion for
initial eruption is not. Latest ages are reported rather than arithmetical means because of the small sample sizes involved.
Among live animal subjects, the deciduous
toothcomb invariably began eruption by the
middle of the second week. Examination of
stillborns indicates that, in fact, the deciduous toothcomb erupts by the time of birth.
Among the tamarins described by Chase and
Cooper (1969) and Glassman (19831, the incisors and canine were present at birth in both
upper and lower jaws.
The upper deciduous canine makes its first
appearance in all species by the end of the
second week. In C. medius, a small (250 gm),
rapidly maturing species, most of the deciduous dentition has erupted by this time, the
only exceptions being the upper incisors. A
similarly rapid pace of deciduous eruption
occurs in l? uerreauxi, where the only teeth
not to have appeared by the end of the second
week are the small central incisor of the up-
per jaw, and the rudimentary lower canine
and dp3 of the lower jaw.
The rapid rate of deciduous eruption in C.
medius is perfectly understandable given its
small size. The comparable rate of deciduous
eruption in l? verreauxi, by contrast, is quite
surprising-it is among the largest of the extant Madagascar lemurs. A possible explanation for the fast pace of deciduous tooth
eruption in the latter species is afforded by
Richard’s (1976) observation of food tasting
in a 2-week-oldwild sifaka. If food tasting or
mastication were characteristic of the species
at this age, it would provide a convincing
reason for the rapid eruption of its deciduous
teeth. Unfortunately, we don’t know if Richard’s finding is indeed accurate for l? uerreauxi or not; all that can be said is that early
ingestion of solid foods has not been reported
in other studies of sifakas, either in the wild
or in captivity (Eaglen and Boskoff, 1978).
Within the genus Lemur, L. catta shows a
more precocious eruption of the deciduous
dentition than do the remaining species. The
deciduous teeth in L. catta have all begun
eruption by the middle of the second month;
in the other species eruption of deciduous
teeth continues into the middle of the third
month. The more rapid rate of deciduous
tooth eruption in L. catta compared to other
Lemur species parallels the generally more
rapid behavioral development and earlier independence of the former species (Klopfer and
Klopfer, 1970; Sussman, 1977).
Permanent eruption sequences
The sequence and timing of eruption of the
permanent dentition is indicated in Table 4.
Sample sizes for these data are much smaller,
as they are based only on the subjects born
during the first year of the study. Eruption
sequences for L. macaco, l? uerreaui, and C.
medius are incomplete because the subjects
were not available for the full term of the
study.
The sequences of permanent tooth eruption, like those of the deciduous dentition,
manifest certain broad patterns across species. For all six species studied, the anterior
permanent molars of each jaw were the first
adult teeth to erupt. This event occurred earliest (1%months) in the smallest species, C.
medius, and from 4 to 6 months of age in the
remaining species. As before, I? uerreauxi and
L. catta erupted M1 at a n earlier age than
did the other Lemur species.
"OOTH ERUPTION IN LEMURS
hli
311
In most Lemur species and in C. medius,
the toothcomb erupted next as a functional
unit, followed by the upper incisors and second molars; the only exception to this pattern
was exhibited by L catta, in which the second molars erupted before the appearance of
the anterior dentition. By the end of the tenth
month, the anterior teeth and first two molars had penetrated the gingiva in all Lemur
species.
This first wave of permanent tooth eruption was followed by a period of stasis in the
genus Lemur. The lag between the eruption
of the anterior teeth and first two molars and
the appearance of the remaining permanent
teeth ranged from 3 to 4 months. By the end
of the twelfth month in L. catta, and the end
of the thirteenth month in other Lemur species, eruption of the permanent premolars
had begun. The sequence of premolar eruption observed in these animals was the same
as that reported by Schwartz (1974): 4-3-2
for
L. catta, and 2-4-3 for the other species.
As Table 4 indicates, the timing of eruption
for the posterior molars and the upper canine
was somewhat variable between species.
Schwartz (1974) noted both interspecific and
intraspecific variation in the sequence of initial eruption for these teeth; no intraspecific
variation was recorded in this study, but
sample sizes were quite small.
The emergence of premolars, M3, and the
upper canine, while not as distinctly patterned as the eruption of the other permanent teeth, nevertheless occurred fairly
rapidly over a period of 3 to 4 months. By 17
months of age, the complete adult dentition
had penetrated the gingiva in all of the Lemur species for which data were available.
The sequence and timing of eruption of the
permanent dentition is similar in some ways
to the eruption of the deciduous dentition. In
most cases, a given mandibular tooth erupts
simultaneously with or earlier than its maxillary counterpart. Eruption of the permanent teeth progresses most rapidly in the
smallest species, C. medius. Within the genus Lemur, the most rapid eruption of the
permanent dentition takes place in L. catta.
The early eruption of M1 in P. verreauxi suggests that this species, like L. catta, also
undergoes rapid tooth eruption compared to
other Madagascar lemurs of comparable size
(e.g., L uariegutus).
The pattern of eruption in Lemur is consistent, with teeth emerging in two distinct
stages. In the earlier stage, 2 to 3 months
312
R.H.EAGLEN
after the deciduous dentition has fully
emerged, the toothcomb, upper incisors, and
first two molars make their appearance.
After a n interval of 3 months or so, the remaining teeth appear in fairly rapid order,
and are in place by the middle of the second
year.
DISCUSSION
The data reported here manifest some correlations with the development of certain aspects of feeding behavior. Among species of
the genus Lemur, the deciduous premolars
erupt during the second month of life; Klopfer and Klopfer (1970) observed that captive
L. catta began tasting solid foods a t the end
of the first month and were ingesting them
by the end of the second month, with L. fulvus and L. variegatus exhibiting a similar
pattern. The period during which solid food
ingestion is initiated and the deciduous premolars erupt is also a time of constant weight
gain for captive Lemur species (Fig. 1).
Once the deciduous premolars have erupted
and growing animals begin displaying a n interest in solid foods, the process of weaning
is initiated. In both captive Lemur species
(Klopfer and Klopfer, 1970) and their wild
counterparts (Sussman, 19771, weaning begins during the middle of the third month of
life. By the middle of the fourth month, young
L. catta are largely independent of their
mothers, and independence is achieved by
young L.. fulvus by the end of the fourth
month. In terms of tooth eruption, this period
of weaning and behavioral independence is a
static one-the only teeth which penetrate
the gingiva during this period are the deciduous upper incisors. Weight gain also increases with no discernible change during
this period (Fig. l), suggesting that the deciduous premolars are suffkiently efficient
during mastication to permit the smooth
transition from a suckling mode of feeding to
a primarily chewing regime.
Eruption of the deciduous premolars may
or may not be associated with the transition
from maternal milk to solid food in I? verreauxi. In this species the deciduous premolars have erupted by the middle of the first
month. As noted earlier, Richard (1976) saw
food tasting in a wild sifaka a t that age.
Among captive sifakas, however, solid food
tasting has not been observed until the middle or late part of the second month (PetterRousseaux, 1962; Albignac, 1969; Eaglen and
Boskoff, 1978). One should also note that the
timing of premolar eruption reported here is
based on a single animal. Thus, the coincidence of deciduous premolar eruption and
the onset of solid food experimentation needs
further documentation to confirm the hypothesis that the two are related in I! uerreauxi.
The emergence of the deciduous toothcomb
a t or near the time of birth probably has no
behavioral significance. While the permanent toothcomb is used both in feeding and
in grooming, neither of these kinds of behavior is manifested by newborn lemurs (except,
of course, suckling). Masticatory activity, as
noted above, does not as a rule begin before
the second month of life; this is probably also
true for grooming behavior. Although the literature on lemur behavior seldom discusses
the development of grooming, the scant
available evidence suggests that it does not
begin during the early postnatal period.
Klopfer and Dugard (1976)first observed selfgrooming in 1,. variegatus during the second
week and a n infant grooming another animal in the fourth week. Eaglen and Boskoff
(1978) did not observe self-grooming in I! verreauxi until the fourth week of life. Since the
corresponding teeth also appear perinatally
in Saguinus fiiscicollis (Glassman, 1983) and
S. nigricollis (Chase and Cooper, 1969), it
seems unlikely that the perinatal eruption of
the deciduous toothcomb among lemurs is in
any way related to the unique functions
which that structure serves among adults.
Little attent.ion has been paid to changes
in feeding behavior after the weaning period
in lemurs; thus, it is impossible to correlate
aspects of permanent tooth eruption directly
with corresponding behavioral events. On the
other hand, the pattern of tooth eruption in
some Lemur species does appear to be linked
with changes in growth rate and resource
utilization which accompany transitions from
wet to dry seasons and vice versa.
During the first 6 months of life, growth
rates are more or less constant for the Lemur
species used in this study (Fig. 1). For the
smaller species (L. catta, L. fulvus, L. macaco), born mainly in the months of September and October in Madagascar, the age at
which the growth rate slows down (among
captive animals) falls near the end of the
rainy season, in the months of March and
April (Martin, 1972). The change in climate
is accompanied by a shift in resource utilization among L. catta and L. fulvus, marked by
greater intake of herbaceous plant parts and
313
TOOTH ERUPTION IN LEMURS
,.
2700-
variegatus
"\
L. c a t t a
/ - ' I
2400-
,---L.
,/
2100-
L . rnacaco
/
/
,=-/
,-*'
L . tulvus
18001
E
2
+
I
2
w
_-' I
,I=
1500-
I'
"
/ I
,,;I
,
-
;- - /=-,"
L
_
, I
1200-
3
900-
600-
300-
8
,~~
,', ,
16
1
24
32
1.'
1II "
,
40
48
I
56
1
64
1
72
1
80
AGE(weeks)
Fig. 1. Growth rate of captive L e m w during the first
year and a half of life, based on recorded weights of
subjects studied over full term of project. Dashed lines
along each curve represent the following periods of tooth
eruption, respectively: (1) eruption of deciduous premo-
lars; (2) stage 1 of permanent tooth eruption (see text for
details); (3) stage 2 of permanent tooth eruption. Arrow
along age scale indicates ages of captive L. catta and L.
fuuluus which correspond to dry season for the wild counterparts of those species.
reduction in the intake of fruit (Sussman,
1974). The first phase of permanent tooth
eruption, in which the anterior molars and
anterior dentitions emerge, spans this transitional period in L. catta and L. fuluus, and
extends into the first half of the dry season.
Thus, the timing of the first phase of permanent tooth eruption, when placed in the context of changing ecological events which
occur during that period among wild Lemur
populations, suggests that the two large anterior molars emerge at a time when they
can most effectively be used to process fibrous foods. The two permanent molars, together with the deciduous premolars, then
serve as the primary battery of masticatory
teeth for the remainder of the dry season,
when no further permanent tooth eruption
takes place.
The hypothesis linking the eruption of the
anterior molars to increased folivory in the
two Lemur species might also apply to P.
uerreauxi, whose diet is almost exclusively
folivorous. In €? verreauxi the anterior permanent molar erupts a t 4 months of age; in
the roughly equal-sized L. variegatus, eruption of the first molar does not occur until 6
months of age. The relatively precocious
eruption of M1 in €? verreauxi compared to
L uariegatus can then be interpreted as a
consequence of the former species' primary
dependence on leaves as food after the wean-
314
R.H. EAGLEN
ing period ends. The age at which sifakas
effect the switch from maternal milk to a
leafy diet is not known in the wild, but locomotor independence probably does occur at
about 4 months of age (Eaglen and Boskoff,
1978). Assuming that independent feeding is
contemporaneous with independent locomotion, the anterior molar of sifakas would appear precisely when needed for mastication.
Whether the foregoing analysis applies to
other lemurs which are seasonally or always
folivorous is unknown. By the same token,
little can be said at this time about the behavioral significance of the timing of permanent tooth eruption in species like L.
variegatus, where little is known of its behavior in the wild.
The second phase of permanent tooth eruption in L. catta, involving the permanent premolars, upper canine, and small posterior
molar, occurs a t about 1 year of age. This
wave of tooth eruption is accompanied by a n
increase in the growth rate (Fig. 1) and corresponds with another period of climatic
change, as the dry season gives way to the
next rainy season. Thus, temporary disruptions of the continuity of the masticatory
tooth row (shedding of deciduous premolars
and their replacement by permanent teeth)
occur as the diet of L. catta is shifting from
tough leaves to more soft fruit. A similar
phenomenon occurs among L. fuluus. In general, then, the timing of permanent tooth
eruption looks to be keyed to changing patterns of resource availability and resource
exploitation in L. catta and L. fuluus. The
similar pattern of tooth eruption and weight
gain evinced by L. macaco suggests the same
hypothesis for that species, although corroborating behavioral data are presently
lacking.
There is one other aspect of permanent
tooth eruption which may have behavioral or
functional significance-the
sequence in
which the permanent premolars erupt.
Schwartz (1975) argued that the sequence of
permanent premolar eruption in Madagascar lemurs provides a useful feature for
lemuroid phylogeny reconstruction. Specifically, he considered the 4-3-2 sequence of
permanent premolar eruption in Hapalemur,
Lepilemur, and some adapids as evidence for
close phylogenetic kinship among those taxa;
under this interpretation, the 4-3-2 sequence
exhibited by Lemur catta represents a
parallelism.
An alternative or concomitant functional
explanation may be equally viable. Every
Madagascar lemur species which is primarily folivorous erupts the posterior permanent
premolar before the anterior premolads); this
assertion holds true for Hapalemur, Lepile
mur, and all extant indriids. Thus, there appears to be a strong correlation between the
sequence of permanent premolar eruption
and the preferred diet of Madagascar lemurs.
Although Lemur catta is not exclusively
folivorous, it does consume large quantities
of leaves during the dry season (Sussman,
1974), and its molar morphology is in many
ways comparable to that of more folivorous
species (Kay et al., 1978). This would appear
to enhance the notion that premolar sequences reflect dietary preferences.
The functional argument is fraught with
problems, however. One has already been
noted; in L catta, the posterior permanent
premolar does not erupt during the dry season but a t its end. A second problem is that
L. fuluus, which eats more leaves than L.
catta, does not erupt the posterior premolar
first. Finally, even if the correlation holds for
most Madagascar lemurs, it does not work
for other primate taxa. Among cebids, the
probably folivorous Brachyteles arachnoides
erupts the permanent premolars in a posteroanterior sequence (della Serra, 19521, like L.
catta and Madagascar folivores. In Alouatta,
which is also folivorous, the posterior premolar is the last to erupt (della Serra, 1952).
The strongly frugivorous Cebus albifions
erupts the permanent premolars in a 4-3-2
sequence, like B. arachnoides (Fleagle and
Schaffler, 1982). Thus, in New World primates there does not appear to be any correlation between premolar eruption sequences
and dietary preference.
In summary, the timing of tooth eruption
among Madagascar lemurs shows some correlations with behavioral events and changing ecological conditions which arise during
the first year and a half of life. The deciduous
toothcomb erupts at or shortly after birth but
is probably not related to any specific behavioral event. The deciduous chewing teeth
erupt at the time when young lemurs are
making the transition from a diet of maternal
milk to one of solid foods. Growth is rapid and
continuous during this period and extends to
approximately 6 months of age among the
smaller species of the genus Lemur.
In L. catta and L. fuluus, permanent tooth
eruption begins and the growth rate slows
down slightly in advance of the dry season,
when leaves gain a n increasing prominence
over fruit in the diets of these species. By the
TOOTH ERUPTION IN LEMURS
315
middle of the dry season the two anterior tellectual stimulus for undertaking the projpremolars and the permanent anterior den- ect in the first place, and special thanks are
tition have erupted; no further eruption oc- warranted for his support.
curs until the onset of the following rainy
LITERATURE CITED
season.
The beginning of the new rainy season is Albignac, R (1969) EMvage d'un jeune propitheque, 16murien folivore de Madagascar. Mammalia 33~341accompanied by a n increase in the growth
343.
rate of juvenile L catta and L. fulvus, and Chase, JE, and Cooper, RW (1969) Physical growth and
coincides with the second wave of permanent
dental eruption in a small population of captive born
individuals. Am. J. Phys. Anthropol. 30:111-116.
tooth eruption, in which the permanent premolars, posterior molars, and upper canine della Serra, 0 (1952) A seqiiencia eruptiva dos dentes
definitivos nos simios Platyrrhina e sua interpretaqso
appear. The advent of the rainy season aufilogenetica. Anais de Facultade de Farmacia e Odougurs a dietary shift toward increasing contologia de Universidade de Sso Paulo I0:215-296.
sumption of fruit and reduction in leaf intake. Eaglen, RH, and Boskoff, K J (1978)The birth and early
development of a captive sifaka, Propithecus uerreulwci
The data discussed here suggest that the
coguereli. Folia Primatol. (Basel) 30t206-219.
timing of tooth eruption can be related to
Fleagle, JG, and Schaffler, MB (1982) Development and
changes in ecology and behavior, a t least for
eruption of the mandibular cheek teeth in Cebus ulbithose lemurs whose behavior is reasonably
frons. Folia Primatol. masel) 38~158-169.
well documented in the wild. At this stage Glassman, DM (1983) Growth and development in the
Saddle-Back Tamarin: The sequence and timing of
such hypotheses must remain tentative; they
dental eruption and epiphyseal union. Am. J. Primaare based on admittedly small samples and
tol. 5.51-59.
require the juxtaposition of data from captive Kay, RF, Sussman, RW, and Tattersall, I(1978) Dietary
animals with events which occur in wild leand dental variations in the genus Lemur, with comments concerning dietary-dental correlations among
mur populations. Corroboration of the hyMalagasy primates. Am. J. Phys. Anthropol. 49:119potheses and their further elaboration will
127.
require broader sampling of tooth eruption Klopfer, PH, and Dugard, J (1976) Patterns of maternal
and growth data, preferably from wild specicare in lemurs. 111. Lemur uuriegutus. Z. Tierpsychol.
40:210-220.
mens, of both primarily frugivorous and priKlopfer, PH, and Klopfer, MS (1970) Patterns of matermarily folivorous Madagascar lemurs.
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to account for the sequence of permanent Martin, RD (1972) Adaptive radiation and behavior of
premolar eruption in lemurs as well as the
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timing of eruption. In this case, however,
there are several lines of counterevidence Petter-Rousseaux, A (1962) Recherches sur la biologie
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presently available which render such a n ac- Relethford,
JH,Coelho, AM, and Lawrence, WA (1982)
count tenuous a t best. Still, if the hypothesis
Brief report: Age estimation from dental eruption in
holds, it can be invoked to account for otherinfant and juvenile baboons (Pupiosp.). Am. J. Primatol. 2~205-209.
wise inexplicable parallel sequences of preA (1976) Preliminary observations on the birth
molar eruption exhibited by seemingly Richard,
and development of Propithecus uerreuuri to the age of
remotely related prosimians such as adapids
six months. Primates 17:357-366.
and ring-tailed lemurs.
Schwartz, JH (1974) Dental Development and Eruption
ACKNOWLEDGMENTS
The research reported here was made possible through the cooperation of the management and staff of the Duke University Center
for the Study of Primate Biology and History; among that group, particular thanks
are due to David E. Anderson and Katy Ahmann. W.P. Luckett provided helpful suggestions for the preliminary version of this
manuscript. R.W. Sussman suggested the
possible relationship between eruption patterns and ecological conditions, for which I
a m grateful. Matt Cartmill provided the in-
in the Prosimians and its Bearing on their Evolution.
Ph.D. thesis, Columbia University.
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premolar region of prosimians and its bearing on their
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Sussman, RW (1974)Ecological distinctions in sympatric
species of lemur. In RD Martin, GA Doyle, and AC
Walker (eds): Prosimian Biology. London: Duckworth,
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Sussman, RW (1977) Socialization, social structure, and
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